1. Technical Field
The invention relates to mechanical drives. More particularly, the invention relates to a weight operated mechanical drive.
2. Description of the Prior Art
Mechanical drives operate all sorts of devices from wind-up toys to grandfather clocks. Such drives come in many forms, but they all must store mechanical energy, whether it be in a compressed spring, in an elevated weight, or in some other form. One requirement of such drives is that they release their stored energy in an even and predictable way. For example, a pendulum operated escapement can be used to control the release of stored energy in a clock mechanism. Another requirement for such drives is that the store of energy be recharged after it has been released through mechanical action. For example, a clock mechanism is wound, e.g. by a key which retensions a spring or by elevating a weight.
Weight operated mechanical drives are well known. Weights have the potential to provide energy to the drive in a consistent fashion. Unlike springs, which do not provide constant torque throughout their range of energy release, a weight ideally provides the same torque throughout its entire range of energy release. This is due to the fact that a spring is constrained by the properties of the material from which it is made and the characteristics of those materials over a wide range of tension, e.g. when the spring is first wound vs. when the spring needs rewinding. In contrast, a weight is only constrained by the force of gravity which, for all intents and purposes, is constant.
Weight operated drives include one or more weights that typically hang suspended from a regulating mechanism. The tension imparted to the regulating mechanism by the pull of gravity on the weight provides the driving force to the mechanism. Thus, the controlled falling of the weight operates the mechanism. Such weight operated mechanical drives are "wound" (a term that is perhaps more properly applied to the tensioning of a spring, but that is used herein in the same sense of storing energy for use by the mechanism) by raising the weight, e.g. by pulling a chain or rope to which the weight is attached. Typically, such winding action momentarily suspends operation of the mechanism because the weight is lifted from the mechanism during a winding sequence. As such, it does not pull on the regulating mechanism during such winding sequence. In most clocks such interruption in operation is of negligible consequence. However, in critical applications, such momentary release of torque on the drive produces an error that, over time, cumulates to an unacceptable degree.
It would be advantageous to provide a weight operated mechanical drive that allowed a weight to impart energy thereto in a consistent fashion, both while the weigh is falling (operating the mechanism) and while the weight is being elevated (wound).